U.S. patent application number 10/428849 was filed with the patent office on 2003-10-30 for thin-film deposition method.
Invention is credited to Takagi, Tomoko, Ueda, Masashi.
Application Number | 20030203124 10/428849 |
Document ID | / |
Family ID | 18503825 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030203124 |
Kind Code |
A1 |
Ueda, Masashi ; et
al. |
October 30, 2003 |
Thin-film deposition method
Abstract
In a thin-film deposition method, a substrate is placed in a
heat chamber having a pressure equal to or higher than an
atmospheric pressure, and the substrate is heated in the heat
chamber by supplying gas having a temperature higher than a room
temperature by forced convection. The heated substrate is
transferred from the heat chamber into a deposition chamber which
is a vacuum chamber connected to the heat chamber directly or
indirectly with a valve interposed therebetween. Then, a thin-film
deposition is carried out on the substrate in the deposition
chamber at a deposition temperature higher than the room
temperature.
Inventors: |
Ueda, Masashi; (Tokyo,
JP) ; Takagi, Tomoko; (Tokyo, JP) |
Correspondence
Address: |
KANESAKA AND TAKEUCHI
1423 Powhatan Street
Alexandria
VA
22314
US
|
Family ID: |
18503825 |
Appl. No.: |
10/428849 |
Filed: |
May 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10428849 |
May 5, 2003 |
|
|
|
09749681 |
Dec 28, 2000 |
|
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Current U.S.
Class: |
427/569 ;
427/573 |
Current CPC
Class: |
C23C 16/54 20130101;
C23C 16/4587 20130101; C23C 16/509 20130101; C23C 16/46
20130101 |
Class at
Publication: |
427/569 ;
427/573 |
International
Class: |
H05H 001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 1999 |
JP |
11-374422 |
Claims
What is claimed is:
1. A thin-film deposition method, comprising: placing a substrate
in a heat chamber having a pressure equal to or higher than an
atmospheric pressure; heating the substrate in the heat chamber by
supplying gas having a temperature higher than a room temperature
by forced convection; transferring the heated substrate from the
heat chamber into a deposition chamber which is a vacuum chamber
connected to the heat chamber directly or indirectly with a valve
interposed therebetween; and carrying out a thin-film deposition on
the substrate in the deposition chamber at a deposition temperature
higher than the room temperature.
2. A thin-film deposition method as claimed in claim 1, wherein in
heating the substrate, said substrate is heated in the heat chamber
at least to the deposition temperature.
3. A thin-film deposition method as claimed in claim 1, wherein
said substrate is used for a solar cell.
4. A thin-film deposition method, comprising: placing a substrate
in a heat chamber having a pressure equal to or higher than an
atmospheric pressure; heating the substrate in the heat chamber by
supplying gas having a temperature higher than a room temperature
by forced convection; transferring the heated substrate from the
heat chamber into a load-lock chamber which is a vacuum chamber
connected to the heat chamber directly or indirectly with a first
valve interposed therebetween; transferring the heated substrate
from the load-lock chamber into a deposition chamber which is a
vacuum chamber connected to the load-lock chamber directly or
indirectly with a second valve interposed therebetween, and
carrying out a thin-film deposition on the substrate in the
deposition chamber at a deposition temperature higher than the room
temperature.
5. A thin-film deposition method as claimed in claim 4, wherein in
heating the substrate, said substrate is heated in the heat chamber
at least to the deposition temperature.
6. A thin-film deposition method as claimed in claim 5, wherein
after transferring the substrate from the heat chamber into the
load-lock chamber, a temperature-decrease prevention mechanism
controls a temperature of the substrate to be equal to or higher
than the deposition temperature in the load-lock chamber.
7. A thin-film deposition method as claimed in claim 4, wherein the
substrate is used for a solar cell.
8. A thin-film deposition method as claimed in claim 1, in heating
the substrate, the gas is heated by a hot source, and circulated by
a blower through a path including baffle plates and the substrate
to heat the substrate.
9. A thin-film deposition method as claimed in claim 4, in heating
the substrate, the gas is heated by a hot source, and circulated by
a blower through a path including baffle plates and the substrate
to heat the substrate.
10. A thin-film deposition method as claimed in claim 6, wherein
after transferring the substrate from the heat chamber into the
load-lock chamber, the temperature-decrease prevention mechanism in
the load-lock chamber heats the substrate as a heater to control
the temperature of the substrate to be equal to or higher than the
deposition temperature.
11. A thin-film deposition method as claimed in claim 8, in heating
the substrate, foreign material is removed from the heated gas by a
filter.
12. A thin-film deposition method as claimed in claim 1, wherein in
carrying out the thin-film deposition, a plasma enhanced chemical
vapor deposition is used where plasma is generated by supplying
high frequency power to a high frequency electrode.
13. A thin-film deposition method as claimed in claim 4, wherein in
carrying out the thin-film deposition, a plasma enhanced chemical
vapor deposition is used where plasma is generated by supplying
high frequency power to a high frequency electrode.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of patent application
Ser. No. 09/749,681 filed on Dec. 28, 2000.
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
[0002] The present invention relates to a thin-film deposition
method for depositing a thin-film on a substrate. A thin-film
deposition method has been widely used for manufacturing an
electronic device such as an LSI (large-scale integrated circuits)
and a display device such as a liquid crystal display. In addition,
the thin-film deposition method may be used for manufacturing a
solar cell.
[0003] The solar cell technology has been conventionally in
practical use for an electronic calculator. The technology is
expected to use as electric power generating technology as energy
problems increase, as seen in New Sunshine Program of MITI
(Ministry of International Trade and Industry, Japan).
[0004] The Solar cell is divided into two types. One is a silicon
solar cell, while the other one is a compound semiconductor solar
cell. The silicon solar cell includes a crystallized solar cell
such as a single crystalline silicon solar cell and a
poly-crystalline silicon solar sell. Further, a great deal of
effort has been made to make an amorphous silicon solar cell
practical. This is because the amorphous silicon solar cell has an
advantage of using a thinner semiconductor layer because of a
higher light absorption coefficient, as well as a lower
manufacturing cost. In addition, the amorphous solar cell is using
an abundant gas as a raw material. Contrarily, the crystal silicon
solar cell is using crystal silicon as a raw material that is a
limited resource.
[0005] In manufacturing the amorphous solar cell, it is necessary
to deposit a thin-film on a substrate made of glass, metal or
resin. Therefore, a thin-film deposition apparatus is used. In the
case of the typical amorphous solar cell, technique of plasma
enhanced chemical vapor deposition (CVD) using a mixture of silane
gas and hydrogen gas is often adopted. For example, a hydrogenated
amorphous silicon film is deposited on a substrate by generating HF
(high frequency) discharge in a mixture of silane gas and hydrogen
gas to decompose the silane.
[0006] In thin-film deposition apparatuses, a temperature of a
substrate that is maintained at a specified value during
deposition, hereinafter called "deposition temperature", is often
higher than a room temperature. In CVD, the deposition temperature
is set higher than the room temperature on purpose that the final
reaction could take place by thermal energy, or, the deposition
rate and the film quality could be improved. In this case, it is
required to provide a process of heating the substrate prior to the
deposition.
[0007] A heat chamber having a radiation lamp-heater therein is
usually used for heating the substrate. The heat chamber is
connected air-tightly with a deposition chamber through a valve.
The substrate is heated in the heat chamber up to the deposition
temperature in vacuum, and is transferred to the deposition chamber
for the film deposition. An internal environment of the apparatus
is often a vacuum pressure of about 10 Pa or lower. Therefore, the
radiation heating is employed, as heat conduction and convection
are not expected to be effective in the chamber.
[0008] A load-lock chamber is often connected with the deposition
chamber so that the deposition chamber is not directly exposed to
the atmosphere. A load-lock chamber having the radiation
lamp-heater is used as the heating chamber.
[0009] However, the above-described radiation heating has problems
as follows. First of all, the radiation heating has a high running
cost as heating efficiency of the radiation heating is lower than
other heating methods. In addition, when a larger substrate is
employed, which often happens in the solar cell manufacture, an
apparatus cost is increased remarkably because many long radiation
lamp-heaters must be provided. Moreover, it is required to consider
an issue of energy-payback-time reduction, in which it is necessary
to produce a solar cell with energy less than the electric energy
the solar cell generates. In this point of view, the radiation
heating is not a favorable method because the energy consumption
easily increases in the manufacturing process.
[0010] In addition, the radiation heating has a problem of having
an overshoot when a feed-back-control of the substrate temperature
is carried out, because the substrate temperature rapidly rises
when irradiation on the substrate starts. That is, the substrate
temperature becomes a target value only after exceeding the target
value. When the overshoot happens, a thermal stress is generated in
the substrate, and the substrate may deform or break, or the stress
might remain in the substrate.
[0011] In addition, it is important to improve the accuracy of
controlling the substrate temperature during the heating to secure
the film quality and the reproducibility. However, it is difficult
to control the substrate temperature with the high accuracy in the
radiation heating. For the high-accuracy control, it is preferable
to measure the substrate temperature by a high-performance
radiation thermometer. Contrarily, it is difficult to measure the
substrate temperature by the radiation thermometer during the
radiation heating, because additional radiant ray reflects on the
substrate surface other than the infrared ray associated with the
substrate temperature.
[0012] It is also possible to measure the substrate temperature by
a thermocouple. However, in many cases, it is difficult to contact
the thermocouple with the substrate. The thermocouple is not
suitable for the high-accuracy temperature measurement. Especially,
when the substrate is placed in a vacuum, a temperature difference
occurs at the contact point between the substrate and the
thermocouple because there is no convection to equalize the
atmospheric temperature, thereby decreasing the measurement
accuracy of the thermocouple.
[0013] In addition, the radiation heating has an essential problem
in the solar cell manufacturing. In a structure of the solar cell,
at least one side of a photovoltaic layer needs an optical
transparent electrode. For example, in manufacturing the amorphous
silicon solar cell, the amorphous silicon film is often deposited
on a TCO (Transparent Conductive Oxide) film formed on the
substrate. The TCO film has a characteristic of high infrared-ray
reflectivity. Therefore, it is very difficult to effectively heat
the substrate having the TCO film using the radiation heating.
[0014] Other than the radiation heating, there is a method of
heating the substrate using the heat conduction. In this method, a
plate with a high thermal conductivity is attached to a backside of
the substrate. This plate is called "backing plate". When the
backing plate is heated, the substrate is heated through heat
transfer by the conduction from the backing plate to the substrate.
However, when the issue of the energy-payback-time reduction is
considered, the backing plate is not used, so this method cannot be
employed. In addition, it is difficult to contact the baking plate
with the substrate sufficiently and uniformly. Therefore, it is
difficult to heat the backing plate method effectively and
uniformly.
[0015] In addition, in the backing plate method, the substrate is
heated only from the backside. As a result, a temperature
difference in the thickness direction occurs when a thick substrate
is used. The substrate may suffer a thermal deformation before
heated up to a required temperature.
[0016] There may be another method of heating the substrate from
both sides by radiation. Even if this method is adopted, it is
difficult to maintain the uniform heating from both sides because
the TCO film on one side of the substrate absorbs little infrared
ray. Particularly, if the substrate is heated in a vacuum pressure
using this method, it is very difficult to heat the substrate
uniformly from both sides because there is little heat transfer
through the convection and the conduction.
[0017] An object of the present invention is to solve problems
described above, and to provide a thin-film deposition method
having an efficient heating process without using the conventional
radiation heating process.
[0018] Further objects and advantages of the invention will be
apparent from the following description.
SUMMARY OF THE INVENTION
[0019] To accomplish the objects, according to the present
invention, a thin-film deposition method including the steps of
placing a substrate in a heat chamber having an inner pressure
equal to or higher than an atmospheric pressure; heating the
substrate in the heat chamber by supplying gas having a temperature
higher than a room temperature through forced convection;
transferring the heated substrate from the heat chamber into a
deposition chamber in a vacuum state and connected directly or
indirectly to the heat chamber through a valve; and carrying out a
thin-film deposition on the substrate in the deposition chamber at
a deposition temperature higher than the room temperature.
[0020] The substrate may be heated up to the deposition temperature
or a temperature higher than the deposition temperature in the heat
chamber.
[0021] Further, according to the present invention, a thin-film
deposition method includes the steps of placing a substrate in a
heat chamber having an inner pressure equal to or higher than an
atmospheric pressure; heating the substrate in the heat chamber by
supplying gas having a temperature higher than a room temperature
through forced convection; transferring the heated substrate from
the heat chamber into a load-lock chamber in a vacuum state and
connected directly or indirectly to the heat chamber through a
valve; transferring the heated substrate from the load-lock chamber
into a deposition chamber in a vacuum state and connected directly
or indirectly to the load-lock chamber through a valve, and
carrying out thin-film deposition on the substrate in the
deposition chamber at a deposition temperature higher than the room
temperature.
[0022] A temperature-decrease prevention mechanism may be provided
in the load-lock chamber to prevent the substrate temperature from
being lower than the deposition temperature.
[0023] To accomplish the objects, the invention presents a
thin-film deposition apparatus, comprising; a deposition chamber
which is a vacuum chamber where thin-film deposition is carried out
on a substrate at a deposition temperature higher than room
temperature, and a heat chamber connected directly or indirectly
with the deposition chamber, wherein the substrate is heated in the
heat chamber under the atmospheric pressure or a pressure higher
than the atmospheric pressure, and the substrate is heated by
supplying gas having a temperature higher than the room temperature
through forced convection.
[0024] To accomplish the objects, the invention also presents a
thin-film deposition apparatus, comprising; a deposition chamber
which is a vacuum chamber where thin-film deposition is carried out
on a substrate at a deposition temperature higher than room
temperature, a load-lock chamber which is a vacuum chamber where
the substrate stays temporarily while the substrate is transferred
from the atmosphere to the deposition chamber, and a heat chamber
where the substrate is heated under the atmospheric pressure or a
pressure higher than the atmospheric pressure, wherein the heat
chamber, the load-lock chamber and the deposition chamber are
connected directly or indirectly in this order interposing a valve,
and the heat chamber has a mechanism to heat the substrate by
supplying gas having a temperature higher than the room temperature
through forced convection.
BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 shows a front sectional view of a thin-film
deposition apparatus;
[0026] FIG. 2 shows a side schematic view of a transfer
mechanism;
[0027] FIG. 3 shows a side schematic view of a deposition
chamber;
[0028] FIG. 4 shows a side schematic view of a heat chamber;
and
[0029] FIG. 5 shows a side schematic view of a load-lock
chamber.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0030] Hereunder, embodiments of the present invention will be
described with reference to the accompanying drawings. FIG. 1 shows
a front sectional view of a thin-film deposition apparatus as a
preferred embodiment of this invention. The apparatus shown in FIG.
1 comprises a deposition chamber 1 where a thin-film deposition is
carried out on substrates 9 at a deposition temperature higher than
room temperature, a couple of load-lock chamber 2 and unload rock
chamber 20 where substrates 9 stay temporarily while substrates 9
are transferred between deposition chamber 1 and an atmosphere, a
heat chamber 3 which heats substrates 9 under a pressure higher
than the atmospheric pressure. Heat chamber 3, load-lock chamber 2,
deposition chamber 1 and unload rock chamber 20 are connected
air-tightly in this order with interposing valves 4. A transfer
mechanism 5 which transfers substrates 9 between the atmosphere and
chambers 3, 2, 1, and 20 is provided.
[0031] Valves 4 open and close the openings provided at each
boundary between chambers 3, 2, 1, and 20 for transferring
substrates 9. As valves 4, a gate-valve is suitable. The gate-valve
is the valve used at a linear vacuum path and can make the path
clear with no obstacle remaining when the valve is opened.
[0032] Deposition chamber 1, load-lock chamber 2 and unload rock
chamber 20 are vacuum chambers, which comprise a pumping system 11,
21, and 201, respectively. Though heat chamber 3 is an airtight
chamber, it has no pumping system.
[0033] The composition of transfer mechanism 5 is described using
FIG. 1 and FIG. 2. FIG. 2 shows a side schematic view of transfer
mechanism 5. Transfer mechanisms 5 is a kind of rack-and-pinion
mechanism. Transfer mechanism 5 is mainly composed of a rack board
51 provided horizontally with rack 50 underneath it and pinion
mechanism 52 that transfer rack board 51 to a horizontal direction,
i.e., vertical to the paper of FIG. 2. Each pinion mechanism 52 is
composed of a number of pinions 521 engaged with rack 50 and motors
522 that rotate each pinion 521 to move rack board 51 horizontally.
Linear guides 54 guiding the movement of rack board 51 are
provided.
[0034] As shown in FIG. 1 and FIG. 2, supports 53 are provided
uprightly on rack board 51. Each support 53 has hooks (not shown)
holding substrates 9. A number of pinions 521 are placed at certain
intervals along the transfer direction. As shown in FIG. 1, pinion
mechanisms 52 are provided at one side of the atmosphere, inside of
heat chamber 3, inside of load-lock chamber 2, inside of deposition
chamber 1, inside of unload rock chamber 20 and the other side of
the atmosphere. Each pinion mechanism 52 is operated in order so
that rack board 51 can be transferred from one side of the
atmosphere to the other side through heat chamber 3, load-lock
chamber 2, deposition chamber 1 and unload rock chamber 20.
[0035] As understood from FIG. 1 and FIG. 2, rack board 51 has a
rectangular shape, whose length direction is the transfer
direction. Substrates 9 also have a rectangular shape. Substrates 9
are held by supports 53, making its surface vertical and its length
direction along the transfer direction. As shown in FIG. 2, six
substrates 9 are arranged and held with one rack board 51 in this
embodiment. When rack board 51 is moved, six substrates 9 held by
supports 53 are transferred at the same time.
[0036] A part of transfer mechanism 5 may be provided outside
chambers 1, 2, 3, and 20. For example, a mechanism magnetically
coupling through a wall of chambers 1, 2, 3, and 20 can be adopted.
An actuator provided at the atmosphere drives a mechanism holding
substrates 9 in chambers 1, 2, 3, and 20. This composition is
preferable because mechanisms that are easy to produce dusts or
contaminant can be provided outside chambers 1, 2, 3, and 20.
[0037] Next, the composition of deposition chamber 1 is described
using FIG. 1 and FIG. 3. FIG. 3 shows a side schematic view of
deposition chamber 1. This embodiment has a composition where an
amorphous silicon film is deposited in deposition chamber 1 by the
HF plasma CVD method. Here, frequencies between LF (Low Frequency)
and UHF (Ultra-High Frequency) are defined as HF (High Efficiency).
Specifically, deposition chamber 1 comprises HF electrodes 12
provided in deposition chamber 1, HF power supplies 13 which apply
HF power to HF electrodes 12 and a gas introduction system 14 which
introduces the gas mixture of silane and hydrogen into deposition
chamber 1.
[0038] HF electrodes 12 are elongated downward from the upper wall
of deposition chamber 1. HF electrodes 12 are formed like antenna.
Each HF electrode 12 is a U-shaped metal rod. Both ends of each HF
electrode 12 are fixed air-tightly with insulation block 15
provided at the upper wall of deposition chamber 1. Both ends of HF
electrodes 12 are connected to HF power supplies 13.
[0039] When HF power supplies 13 apply the HF power to HF
electrodes 12 in a state of the gas mixture of silane and hydrogen
introduced by gas introduction system 14, HF discharges are
generated in the gas mixture to form plasmas. Silane decomposes in
the plasmas, resulting in that the hydrogenated amorphous silicon
film is deposited on the surface of the substrate 9 placed on both
sides of HF electrodes 12.
[0040] Points greatly characterizing this embodiment are in the
composition of heat chamber 3. These points are described as
follows using FIG. 4. FIG. 4 shows a side schematic view of heat
chamber 3.
[0041] One point greatly characterizing this embodiment is that the
means of heating is provided not in load-lock chamber 2 but
separately provided in heat chamber 3. The means of heating in this
embodiment is a heating mechanism 31 provided in heat chamber 3.
Another point greatly characterizing this embodiment is that
substrates 9 are heated at a pressure higher than the atmospheric
pressure utilizing forced convection.
[0042] Specifically, heat chamber 3 comprises valves 4 at each
boundary to the atmosphere and to load-lock chamber 2. Pressurizing
gas supply system 32 that supplies compressed air or dry air into
heat chamber 3 to pressurize it is provided. Heating mechanism 31
in heat chamber 3 is composed mainly of heat source 311, baffle
plates 312, 313, 314, and 315 that form an air flow path, and air
blower 316 blowing air through the air flow path for circulating
inside heat chamber 3.
[0043] Heat source 311 has high energy efficiency such as
combustion equipment used with a boiler. Heat source 311 produces
heat of 4000 joule/second, i.e., 60000 Kcal/hour, using City gas as
fuel. Instead of City gas, liquefied petroleum gas (LPG) may be
used as fuel. A centrifugal turbo fan is used as air blower 316.
Baffle plate 312 (hereinafter called the first baffle plate 312)
separates the region at which substrates 9 are placed and the
region at which heat source 311 is provided. Heat source 311 is put
between baffle plate 312 and baffle plate 313 (hereinafter called
the second baffle plate 313). Baffle plate 314 (hereinafter called
the third baffle plate 314) shuts the space between the upper end
of the first baffle plate 312 and the upper end of the second
baffle plate 313. Baffle plate 315 (hereinafter called the fourth
baffle plate 315) shuts the space between the bottom end of the
second baffle plate 313 and the wall of heat chamber 3.
[0044] Second baffle plate 313 is provided with a circulation hole
317. Air blower 316 is fixed on the sidewall of heat chamber 3 at
the same height as circulation hole 317. When air blower 316 is
operated, air heated by heat source 311 is introduced into the
upper space through circulation hole 317.
[0045] Filter 33 is provided above the region where substrates 9
are placed. Filter 33 is flush with the third baffle plate 314 at
its bottom end. Filter 33 traverses the air flow path. Heated air
blowing from air blower 316 flows between the third baffle plate
314 and the upper wall of heat chamber 3, and reaches the space
above filter 33. The heated air flows to substrates 9 through
filter 33 knocking on the wall of heat chamber 3, so that
substrates 9 are heated.
[0046] Filter 33 is used to prevent substrates 9 from
contamination. A HEPA filter (High-Efficiency Particle Air filter)
with heat-resistance up to about 250.degree. C. is preferably used
as filter 33. A heat insulator is provided at the wall of heat
chamber 3 if necessary.
[0047] As designated by arrows in FIG. 4, the heated air heats
substrates 9, when it flows down from the upper space to the bottom
space. Then, the air reaches between the first baffle plate 312 and
the second baffle plate 313, knocking on the bottom wall of heat
chamber 3. Consequently, the air is heated again by heat source 311
and blows out from air blower 316. Rack board 51 and pinion
mechanism 52 are designed to pass the heated air sufficiently.
[0048] Substrates 9 are heated higher than the deposition
temperature by heating mechanism 31 as described. Showing an
example, in case the amorphous silicon film is deposited, the
deposition temperature is about 200.degree. C. In this case,
substrates 9 must be heated in heating chamber 3 up to about
230.degree. C. Heating mechanism 31 is designed so that the
temperature of the heated air can become about 250.degree. C. and
the flow rate of the heated air can be maintained at about 100
m.sup.3 per minute. With this composition, substrates 9 are heated
up to about 230.degree. C. within ten to fifteen minutes.
[0049] On the other hand, in this embodiment, a
temperature-decrease prevention mechanism 22 is provided in
load-lock chamber 2. Temperature-decrease prevention mechanism 22
prevents the substrate temperature from decreasing lower than the
deposition temperature. This point is described using FIG. 1 and
FIG. 5. FIG. 5 shows a side schematic view of load-lock chamber
2.
[0050] Radiation lamp-heaters 221 are employed as
temperature-decrease prevention mechanism 22 in this embodiment.
Radiation lamp-heaters 221 are rod-shaped filament lamps such as
halogen lamps. Radiation lamp-heaters 221 are posed horizontally
and aligned vertically. Radiation lamp-heaters 221 are held at both
ends together with holders 222 in which a feeding line is provided.
Units of radiation lamp-heaters 221 and a couple of holder 222 are
arranged between two substrates 9 and between a substrate 9 and the
wall of load-lock chamber 2.
[0051] When the infrared absorption coefficient of substrates 9 is
poor such as in the case substrates 9 have a TCO film as described,
it is difficult to heat substrates 9 by radiation lamp-heaters 221.
However, in this embodiment, the heating in load-lock chamber 2 is
supplementary because heating mechanism 31 in heat chamber 3 heats
substrate 9 higher than the deposition temperature. In other words,
heating is enough if the substrate temperature does not become
lower than the deposition temperature while substrates 9 stay in
load-lock chamber 2. Considering this point, radiation lamp-heaters
221 are employed as temperature-decrease prevention mechanism 22 in
this embodiment.
[0052] Showing a more-detailed example, about fifteen lamps of
about 1 kW are used for each substrate 9 as temperature-decrease
prevention mechanism 22, in case that substrates 9 are heated up to
about 230.degree. C. in heat chamber 3, the deposition temperature
is 200.degree. C., and substrates 9 are placed in load-lock chamber
2 for about nine minutes. In this example, the pressure in
load-lock chamber 2 is about 1 Pa.
[0053] Heating quantity of radiation lamp-heaters 221 is decided
according to how high temperature substrates 9 are heated to in
heat chamber 3. In addition, it should be considered how much the
substrate temperature decreases by heat dissipation while
substrates 9 are transferred from heat chamber 3 to deposition
chamber 1, and how much heat substrates 9 receive from radiation
lamp-heaters 221 of temperature-decrease prevention mechanism 22 in
load-lock chamber 2. It is preferable that the substrate
temperature is just the same as the deposition temperature when
substrates 9 reach deposition chamber 1.
[0054] Next, whole operation of the apparatus of this embodiment is
described.
[0055] To begin with, substrates 9 are set to rack board 51 at a
platform (not shown). Each support 53 holds substrates 9. After the
valve 4 on the atmosphere side of heat chamber 3 is opened,
transfer mechanism 5 is operated to transfer substrates 9 into heat
chamber 3. The pressure in heat chamber 3 is always maintained a
little higher than the atmospheric pressure by pressurizing gas
supply system 32.
[0056] After closing the valve 4, air blower 316 is operated to
cause the forced convection, thereby heating substrates 9. Heat
source 311 is operated all the time while the apparatus is
available. Air blower 316 may be operated all the time as well.
[0057] After heating substrates 9 up to a specified temperature, a
valve on pressurizing gas supply system 32 is closed. Substrates 9
are transferred to load-lock chamber 2 after valve 4 between heat
chamber 3 and load-lock chamber 2 is opened. After closing the
valve 4, load-lock chamber 2 is pumped by pumping system 21 to a
specified vacuum pressure. Substrates 9 are transferred to
deposition chamber 1 after valve 4 between load-lock chamber 2 and
deposition chamber 1 is opened.
[0058] Next, after the valve 4 is closed the deposition onto
substrates 9 is carried out in deposition chamber 1 as described.
Substrates 9 are transferred out to the atmosphere via unload-lock
chamber 20 after the deposition. Substrates 9 are taken out from
each support 53 on rack board 51 at another platform (not
shown).
[0059] The apparatus of this embodiment described above brings a
merit that the energy efficiency is higher and the running cost is
lower because heating mechanism 31 provided in heat chamber 3 heats
substrates 9 not by the radiation but by the forced convection.
Particularly, the apparatus of this embodiment is suitable for the
manufacture of solar cells for power supply because it requires the
energy-payback-time reduction.
[0060] Substrates 9 are heated sufficiently even if those infrared
ray absorption coefficients are poor as in case of the substrate
with the TCO film, because substrates 9 are heated not by the
radiation but by the forced convection. This point is another
reason why this embodiment is suitable for the manufacture of solar
cells.
[0061] Problems of the overshoot and the thermal deformation of
substrates 9 do not arise in this embodiment, because substrates 9
are not heated rapidly as in case of the radiation heating. In
addition, it is possible to measure the substrate temperature with
high accuracy by a radiation thermometer. Therefore, the
temperature control of substrates 9 can be carried out with high
accuracy.
[0062] The composition where substrates 9 are heated to a
temperature higher than the deposition temperature also contributes
to enhancing energy efficiency. It is possible to heat substrates 9
at a temperature lower than the deposition temperature in heat
chamber 3 and thereafter heat substrates 9 up to the deposition
temperature in load-lock chamber 2 or deposition chamber 1.
However, it is difficult to heat substrates 9 efficiently in
load-lock chamber 2 or deposition chamber 1 because those are
vacuum chambers where the convection heating cannot be utilized.
Therefore, heating in load-lock chamber 2 or deposition chamber 1
must be the radiation heating. As described, the radiation heating
has the low energy efficiency. The radiation heating of the
substrate with the TCO film is essentially impossible. Contrarily,
when substrates 9 are heated higher than the deposition temperature
in heat chamber 3 as in this embodiment, the radiation heating of
the low efficiency is not required. Therefore, even the substrate
with the TCO film can be heated sufficiently.
[0063] The merit of film quality improvement is brought from the
composition that substrates 9 are transferred to deposition chamber
1 via load-lock chamber 2 after substrates 9 are heated to a
temperature higher than the deposition temperature in heat chamber
3. To heat substrates 9 in heat chamber 3 brings the significance
that adsorbed gas can be released sufficiently from substrates 9.
Gas such as vapor is adsorbed to the surface of substrates 9. If
the deposition is carried out in a state that adsorbed gas such as
vapor has not been well released, adsorbed gas would be released
rapidly to contaminate the deposited film or to cause a structural
defect such as forming bubbles within it. When substrates 9 are
heated prior to the deposition, these problems are prevented since
adsorbed gas is well released in advance.
[0064] Now, how much quantity of adsorbed gas is released depends
on how high temperature substrates 9 are heated and how long the
temperature is kept. In this embodiment, substrates 9 are heated
higher than the deposition temperature in heating chamber 3 and
transferred to deposition chamber 1 via load-lock chamber 2,
keeping almost the same temperature. Therefore, adsorbed gas is
well released from substrates 9 by the time when substrates 9
arrive at deposition chamber 1. Contrarily, if the adsorbed gas
release is carried out only by the heating in load-lock chamber 2,
gas release is insufficient because high-temperature keeping time
gets shorter. In this case, substrates 9 need to stay longer in
load-lock chamber 2 so that adsorbed gas can be well released,
resulting in that the productivity decreases and the running cost
increases. Therefore, this composition is not preferable.
[0065] Another merit that substrates 9 are not required to be
heated at so high temperature in heat chamber 3 is brought from the
composition that temperature-decrease prevention mechanism 22 is
provided in load-lock chamber 2. If temperature-decrease prevention
mechanism 22 is not provided, there arises necessity to heat
substrates 9 at so high temperature calculating the temperature
decrease in load-lock chamber 2. In this composition, it would take
longer time to heat substrates 9 in heat chamber 3. Otherwise,
heating mechanism 31 would be required to be larger size. The cost
of providing temperature-decrease prevention mechanism 22 and the
running cost of this embodiment possibly would be lower than
that.
[0066] Moreover, another merit that substrates 9 can be restrained
from contamination while those are transferred from heat chamber 3
to deposition chamber 1 is brought from the composition that heat
chamber 3 is a part of the apparatus, i.e., heat chamber 3 and
deposition chamber 1 are connected air-tightly. If substrates 9 are
temporarily taken out from the apparatus while those are
transferred from heat chamber 3 to deposition chamber 1, substrates
9 may suffer from contamination such as adhesion of contaminants.
The possibility of contamination is low when heat chamber 3 is
connected with deposition chamber 1 directly or indirectly as shown
in this embodiment.
[0067] It is possible to employ a chamber layout of the
cluster-tool types where load-lock chamber 2, heat chamber 3 and
deposition chamber 1 are provided around a transfer chamber in
which a transfer robot is provided.
[0068] It is also possible to employ the composition where
substrates 9 are heated just at the deposition temperature, though
those are heated higher than the deposition temperature in this
embodiment. The pressure in heat chamber 3 may be the same as the
atmospheric pressure. Still, the pressure higher than the
atmospheric pressure brings the advantage that contaminants would
not be introduced into heat chamber 3. Inert gas such as nitrogen
may be supplied into heat chamber 3 instead of compressed air or
dry air at a pressure higher than the atmospheric pressure.
[0069] A ceramic heater may be used as temperature-decrease
prevention mechanism 22 instead of radiation lamp-heaters 221. The
heating in load-lock chamber 2 can be eliminated by heating
substrates 9 in heat chamber 3 at a temperature higher enough than
the deposition temperature. A specified heat-insulation mechanism
may be used as temperature-decrease prevention mechanism 22 in load
loch chamber 2.
[0070] Other than the hydrogenated amorphous silicon film
deposition as described, the apparatus of the invention can carry
out another amorphous silicon film deposition such as amorphous
silicon fluoride film deposition, amorphous silicon carbide film
deposition, amorphous silicon germanium firm deposition and the
like. Phosphorus doped films or boron doped films also can be
deposited by the apparatus of the invention.
[0071] The apparatus of the invention can be used for manufacture
of liquid crystal displays or information storage disks other than
solar cells. For example, the composition of the heating in this
invention can be used for a thin-film deposition for a driver
electrode in an LCD. Especially, sufficient gas release is required
when an indium-tin-oxide (ITO) film is deposited by sputtering on a
substrate with a color filter formed on it, because the color
filter involves much water. Therefore, the apparatus of the
invention that can carry out the gas release efficiently is
suitable.
[0072] The composition of deposition chamber 1 is optimized
according to a kind of deposition process. For example, a CVD not
by an inductive coupled plasma but by a capacitive coupled plasma
may be adopted. Physical depositions such as sputtering or ion-beam
deposition can be adopted as well.
* * * * *